This invention relates generally to a process of recovering copper from ores containing copper as oxides, and more particularly, the invention relates to a process for recovering copper from ores containing atacamite/paratacamite utilizing a novel combination of flotation agents for the copper.
Copper minerals in the oxidized zone of porphyry copper deposits are categorized broadly as copper "oxides". These oxides include atacamite/paratacamite [Cu.sub.2 (OH).sub.3 Cl], azurite/malachite [Cu.sub.3 (CO.sub.3).sub.2 (OH).sub.2 /Cu.sub.2 (CO.sub.3)(OH).sub.2 ], chrysocolla [CuSiO.sub.3.nH.sub.2 O], cuprite [Cu.sub.2 O], etc. The copper minerals in the underlying sulfide rich and primary sulfide zones include chalcocite [Cu.sub.2 S], chalcopyrite [CuFeS.sub.2 ], and bornite [Cu.sub.5 FeS.sub.4 ].
One commonly used method for concentrating copper sulfide minerals utilizes a froth flotation circuit utilizing known sulfide collectors. However, the normally used collectors for sulfide minerals generally will not react upon the "oxide" copper minerals, and, hence, the recovery of copper from the copper oxide minerals often requires treatment steps which are different from those used with the sulfide ores.
Xanthates have been described as collectors for copper in froth-flotation procedures, but not all copper ores respond favorably to the xanthate collectors. U.S. Pat. No. 3,901,450 describes a flotation process for copper from ores containing copper sulfides wherein the suspension is conditioned in the presence of an alkaline agent and an alkali metal xanthate at a pH of from about 9.5 to about 12 and thereafter conditioned in the presence of selected dispersing agents and flocculating agents. U.S. Pat. No. 3,667,690 also describes a process for flotation of sulfide minerals from their ores utilizing two or more conditioning steps prior to the froth flotation step, and one of the conditioning steps utilizes a member of the xanthate family of flotation reagents and a dispersing agent.
The recovery of chrysocolla and iron oxide minerals from their ores by flotation utilizing hydroxamic acids as chelating agents for the copper is described in U.S. Pat. No. 3,438,494. The combination of hydroxamic derivatives such as potassium octylhydroxamate with amyl xanthate is disclosed as being useful although the inventors found that the copper minerals floated with the use of the hydroxamate alone.